Precise Point Positioning Using Dual-Frequency GNSS Observations on Smartphone

Abstract

The update of the Android system and the emergence of the dual-frequency GNSS chips enable smartphones to acquire dual-frequency GNSS observations. In this paper, the GPS L1/L5 and Galileo E1/E5a dual-frequency PPP (precise point positioning) algorithm based on RTKLIB and GAMP was applied to analyze the positioning performance of the Xiaomi Mi 8 dual-frequency smartphone in static and kinematic modes. The results showed that in the static mode, the RMS position errors of the dual-frequency smartphone PPP solutions in the E, N, and U directions were 21.8 cm, 4.1 cm, and 11.0 cm, respectively, after convergence to 1 m within 102 min. The PPP of dual-frequency smartphone showed similar accuracy with geodetic receiver in single-frequency mode, while geodetic receiver in dual-frequency mode has higher accuracy. In the kinematic mode, the positioning track of the smartphone dual-frequency data had severe fluctuations, the positioning tracks derived from the smartphone and the geodetic receiver showed approximately difference of 3–5 m.

Real-Time Geophysical Applications with Android GNSS Raw Measurements

“…The availability of GNSS measurements from such mass-market devices encourages researchers to extend the use of traditional algorithms that were originally developed for high-end receivers to include this new generation of GNSS devices, aiming mainly at increasing the positioning accuracy. Real-time kinematic (RTK) and Precise Point Positioning (PPP), for example, are widely used to exploit the benefits coming from the accessibility of the raw GNSS measurements [1][2][3][4]. However, high accuracy is prevented by the quality of GNSS measurements obtainable from Android smartphones, due especially to the characteristics of the GNSS antenna: shared with other communication systems (WiFi, Bluetooth, etc.…”

The problem of GNSS positioning with measurements recorded using Android mobile devices

“…In addition, the reliability of measurements leaves much to be desired, especially when they are taken at a point surrounded by field obstacles. Smartphone GNSS antennas use linear polarisation, showing susceptibility to multipath effects [5], [7]. In addition, the characteristics of phase centre variation of antennas used in mobile devices have not yet been determined.…”

“…In this case, the effect of phase centre variation should be significantly reduced. As the authors of the quoted papers [7] [23] observe, measurements using smartphones are characterised by frequent occurrence of the so called "cycle slips." This problem has been the subject of numerous publications describing effective methods of detection and repair of "cycle slips" [24], [25] [26].…”

“…This leads to the so-called "cycle slips", making it difficult or impossible to resolve cycle ambiguity in GNSS phase measurements [5]. Starting from Android version 9.0, it is possible to disable the "duty cycle" from the API level [7].…”

“…The publication [7] presents tests using the PPP (Precise Point Positioning) method [3]. The experiment used a Xiaomi Mi8 smartphone, located on the roof of a building, in good observation conditions.…”